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Stop determination apparatus, inclination determination apparatus, and electric parking brake controllerStop determination apparatus, inclination determination apparatus, and electric parking brake controller description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070173984, Stop determination apparatus, inclination determination apparatus, and electric parking brake controller. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001]1. Field of the Invention [0002]The present invention relates to a stop determination apparatus for determining whether a vehicle such as an automobile is at a standstill, an inclination determination apparatus for determining an inclination of the road surface on which the vehicle such as an automobile is stopped, and an electric parking brake controller which incorporates both these apparatuses. [0003]The present application claims each priority from Japanese Patent Application Nos. 2006-001667, 2006-051635, and 2006-274991, the respective disclosures of which are incorporated herein by reference. [0004]2. Description of the Related Art [0005]An electric parking brake actuates a parking brake during vehicle parking or stopping using, for example, an electric actuator such as a motor. Such an electric parking brake can be operated by a vehicle operator using electrical switches, thus allowing reduced operator efforts when compared to a manual lever or foot brake pedal. [0006]It has also been suggested that the electric parking brake be provided with an additional hill-hold (hill-holder) function. The hill-hold function serves to automatically actuate the electric parking brake when the vehicle is stopped on an inclined road surface, in order to prevent unintentional movement of the vehicle. To fully realize such a hill-hold function, a reliable determination must be made as to whether the vehicle is at a standstill. [0007]Vehicles are known which are provided with a vehicle speed sensor for detecting the rotational speed of the drive wheels and which utilize its output for determination of a stop of the vehicle. However, such a vehicle speed sensor cannot accurately detect the speed of the vehicle running at an extremely low speed immediately before the vehicle is being stopping. For example, it may be impossible to detect when the vehicle is running at an actual speed of about 2 km/h or less. In this regard, one type of conventionally known electric parking brakes is configured so that a timer is activated when the vehicle speed sensor detects a speed of 2 km/h or less immediately before the vehicle is stopped. Then, the vehicle is determined to be at a standstill after a predetermined period of time has elapsed, and the brakes are applied (for example, see Japanese Patent Application Laid-Open Publication No. 2004-142517). [0008]However, with this conventional technique, the determination of a stop of the vehicle is made only on the basis of this elapsed period of time after the vehicle speed cannot be detected. This may readily allow a difference between the time at which the vehicle is actually brought to a standstill and the time at which the vehicle is determined to be at a stop. The difference would in turn sometimes result in the electric parking brake being activated even when the vehicle has not yet actually stopped. Conversely, the difference would also sometimes allow the vehicle to start to roll onward after the vehicle has been stopped due to a time lag between the stop thereof and the activation of the electric parking brake. This time lag might, for example, be up to about 2 seconds, and thus needs to be improved. [0009]Furthermore, using this conventional technique, it is difficult to accurately estimate the timing of a stop. If any acceleration of the vehicle unexpectedly occurs after the vehicle is determined to have stopped, a G sensor (acceleration sensor), which is normally used to determine the inclination of a road surface, would detect this acceleration and incorporate it into an erroneous determination of the inclination of the road surface. [0010]Furthermore, different braking forces are required for the hill-hold function depending on the inclination (slope) of a road surface on which the vehicle is stopped. For example, on a steep hill, a larger braking force is required to prevent unintentional movement of the vehicle. However, producing such a larger braking force every time would cause an increased burden on the device under normal conditions of use as well as an increase in the power required for activation. In regard to this, an electric parking brake is also known which is provided with an inclination sensor for detecting the inclination of a road surface with an acceleration (G) sensor, to change the braking force in response to the output therefrom (for example, see aforementioned Japanese Patent Application Laid-Open Publication No. 2004-142517). [0011]However, during deceleration of the vehicle or immediately after a stop of the vehicle, the inclination sensor using the G sensor will detect a deceleration G or a longitudinal G caused by pitching of the vehicle or the like, and thus cannot properly determine the inclination. Thus, this will cause a time lag of, for example, about 2 seconds after the vehicle has stopped before the determination of the inclination can be completed. This in turn will cause a time lag between the stop of the vehicle and the activation of the electric parking brake. Thus, for example, after the vehicle has been stopped on an inclined road, the user must keep the brake pedal depressed for a period of time corresponding to this time lag. Thus, further improvement in operability is desired. SUMMARY OF THE INVENTION [0012]The present invention was developed to overcome these problems. It is therefore an object of the present invention to provide a stop determination apparatus which is capable of making a proper determination of a stop of a vehicle, an inclination determination apparatus which is capable of making a quick determination of the inclination when the vehicle is stopped, and an electric parking brake controller which includes these apparatuses. [0013]The present invention achieves the aforementioned object by the following solutions. [0014]A first aspect of the present invention relates to a vehicle stop determination apparatus for determining whether a vehicle is at a standstill, which includes: a vehicle speed sensor for detecting a speed of a vehicle; a G sensor for detecting a longitudinal acceleration of the vehicle; an inclination acceleration estimate section for calculating an estimated inclination acceleration resulting from an inclination of a road surface based on a vehicle speed reduction rate calculated from an output of the vehicle speed sensor and an output from the G sensor; and a stop determination section which has a first stop determination mode and a second stop determination mode and which selects the first stop determination mode or the second stop determination mode based on the vehicle speed reduction rate calculated before the output of the vehicle speed sensor falls below a detection limit. Then, in the first stop determination mode, a stop of the vehicle is determined based on a change in the output of the G sensor when the output of the vehicle speed sensor is equal to or less than the detection limit, and in the second stop determination mode, the output of the G sensor and the estimated inclination acceleration are compared to each other to determine a stop of the vehicle. [0015]In addition to the first aspect of the present invention, in the first stop determination mode, the determination of a stop may be made based on a change in the output of the G sensor from a decelerating side to an accelerating side. Alternatively, the determination of a stop may be made according to a convergence in variations in the output of the G sensor. Furthermore, in the first stop determination mode, the determination of a stop may be established when variations in the output of the G sensor are equal to or less than a pre-defined threshold value over a predetermined period of time. [0016]Furthermore, the vehicle stop determination apparatus may include an estimated stop time computation section for calculating an estimated stop time based on the detection limit and the vehicle speed reduction rate when the output of the vehicle speed sensor is equal to or less than the detection limit. The stop determination section may further have a third stop determination mode in which a stop of the vehicle is determined after the estimated stop time elapses. Furthermore, the stop determination section may further have a fourth stop determination mode in which a stop of the vehicle is automatically determined regardless of the stop determination determined by the first step determination mode and the second step determination mode when the output of the vehicle speed sensor is equal to or less than the detection limit over a predetermined stand-by time period. [0017]Furthermore, an electric parking brake controller having the vehicle stop determination apparatus according to the first aspect of the present invention includes an electric parking brake control section for controlling an electric actuator to change braking force of a parking brake and thereby switching the electric actuator between a braking state and a released state of the parking brake. When the vehicle stop determination apparatus establishes a determination of a stop of the vehicle, the electric parking brake control section allows the parking brake to transition into the braking state. [0018]A second aspect of the present invention relates to an inclination determination apparatus for determining an inclination of a road surface on which a vehicle is stopped, the inclination determination apparatus including: a vehicle speed sensor for detecting a speed of a vehicle; a G sensor for detecting a longitudinal acceleration of the vehicle; an inclination determination section for calculating an estimated inclination acceleration resulting from an inclination of a road surface based on a vehicle speed reduction rate calculated from an output of the vehicle speed sensor and an output from the G sensor; and a stop determination section for determining a stop of the vehicle based on the output of the vehicle speed sensor. The inclination determination section determines the inclination to be a flat surface if the estimated inclination acceleration is below a predetermined criterion value, and re-determines the inclination based on the output of the G sensor when the stop determination section establishes a determination of a stop of the vehicle. [0019]A third aspect of the present invention relates to an electric parking brake controller including the inclination determination apparatus according to the second aspect of the present invention and an electric parking brake control section for controlling an electric actuator to change braking force of a parking brake. When the stop determination section establishes a determination of a stop of the vehicle, the electric parking brake control section sets the braking force of the parking brake based on an estimated inclination acceleration calculated by the inclination determination section. [0020]The present invention can provide the following effects. [0021](1) During deceleration, the vehicle is in a state in which the front suspension is compressively (contractively) stroked (nosedived), whereas when the vehicle stops, the front suspension is expansively stroked due to its repulsive force. Since this will result in a change in behavior in the direction of pitching, a stop of the vehicle can be determined based on such a change in behavior in the direction of pitching. This makes it possible to accurately determine the stop of the vehicle even when the vehicle is at an extremely low speed equal to or less than the speed detection limit of the vehicle speed sensor. [0022](2) A determination of a stop of a vehicle can be made with further improved accuracy by using an estimated stop time calculated based on a deceleration of the vehicle in addition to the change in behavior of the vehicle in the direction of pitching of the vehicle. Continue reading about Stop determination apparatus, inclination determination apparatus, and electric parking brake controller... Full patent description for Stop determination apparatus, inclination determination apparatus, and electric parking brake controller Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Stop determination apparatus, inclination determination apparatus, and electric parking brake controller patent application. 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